FIG. 5 shows a structural outline of a conventional axis flow type gas laser oscillator. The conventional axis flow type gas laser oscillator is explained hereinafter by referring to FIG. 5.
In FIG. 5, discharge tube 1 is made of dielectric material such as glass. Electrodes 2 and 3 are placed at circumference of discharge tube 1. Power source 4 is connected to electrodes 2 and 3. Discharge space 5 is an empty space allocated between electrodes 2 and 3 inside discharge tube 1. Discharge part 40 includes discharge tube 1, electrodes 2 and 3, power source 4, and discharge space 5. Fully reflective mirror 6 and partially reflective mirror 7 are placed at both ends of discharge space 5, constituting the optical oscillator. Laser beam 8 is issued from partially reflective mirror 7. Arrow mark 9 indicates a direction of laser gas flow circulating in the gas laser oscillator. Laser gas flow pipe 10 indicates a flow route of laser gas. Heat exchangers 11 and 12 reduce a temperature of the laser gas heated by an electric discharge in discharge space 5 and a movement of an air blower. Air blower 13 circulates laser gas in discharge space 5 at a flow speed of about 100 m/sec. Laser gas flow pipe 10 and discharge tube 11 are connected at laser gas introduce part 14.
Following, working mechanism of the conventional gas laser oscillator is explained.
Laser gas introduce part 14 introduces laser gas blown by air blower 13 into discharge tube 1 through laser gas flow pipe 10. The electrodes 2 and 3 connected to power source 4 discharge electricity in discharge space 5. Laser gas is excited in discharge space 5 by receiving the discharged electric energy. The excited laser gas becomes an oscillating state in the optical oscillator composed of fully reflective mirror 6 and partially reflective mirror 7, emitting laser beam 8 from partially reflective mirror 7. Thus produced laser beam 8 is used for laser processing.
FIG. 6 is a structural diagram of the conventional gas laser oscillator illustrated with an air blower and its vicinity. Air blower 13 is fixed to driving part 22 via shaft 23. Air blower 13 and driving part 22 are separated by divide wall 24. A several ten μm of space is made around shaft 23 for not obstructing rotation of the shaft.
With this kind of conventional gas laser oscillator, the gas is dissociated by the electric discharge so is deteriorated with an elapse of time. Because of this reason, the laser gas is partially ejected from gas flow pipe 10 at any time by main ejection apparatus 25.
Driving part 22 contains oil 33 for lubricating the driving part. If mist of the oil (hereafter called ‘mist’) is dispersed into the laser gas in the gas circulating part, purity of the gas is lowered causing a serious malfunction during laser oscillation. To prevent the oil mist to move into air blower 13 through divide wall 24, a pressure in driving part 22 needs to be lower than that of in air blower 13 at any time.
Gas supply apparatus 29 is connected to laser gas flow pipe 10 for supplying an equivalent amount of ejected laser gas. Sub ejection apparatus 26 ejects laser gas from driving part 22. Namely, the conventional gas laser oscillator has two ejecting apparatus, main ejection apparatus 25 and sub ejection apparatus 26, and both gas ejecting apparatus are connected to vacuum pump 27.
As described, with the conventional gas laser oscillator, the laser gas is drawn out of driving part 22 and a pressure inside driving part 22 is made lower than where air blower 13 is, and such state is identified. A constitution of above mentioned conventional gas laser oscillator is disclosed in Japanese Patent Unexamined Publication No. 2000-22243 and No. 2003-110170, for examples.
In the conventional gas laser oscillator, however, sub ejection apparatus 26 draws gas what is mixed with oil mist from driving part 22, so that liquefied oil is deposited inside the laying pipe and then is solidified, clogging the pipe with an elapse of time. The clogged pipe reduces an amount of gas ejected through sub ejection apparatus 26, causing an insufficient ejection of gas from driving part 22. Consequently, a difference in pressure between driving part 22 and air blower 13 becomes smaller, increasing a possibility of oil mist in driving part 22 entering into air blower 13. The laying pipe of the sub ejection apparatus clogged with a lapse of time can be cleaned easily as long as a proper maintenance work is conducted, so how fast to detect a clogging of the pipe is a possible problem.